After a fight with her boyfriend, Mami, the younger sister, ends up at her older sister's place. This is her first encounter with her sister's boyfriend. Intrigued by his shy and earnest demeanor, she playfully teases him, unwittingly igniting his libido. From that day on, she finds herself constantly craving more sex. She discovers that his quick-ejaculating, insatiable cock never seems to run out of steam, relentlessly pounding her pussy until she's begging for mercy!